News and notes about science

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People practice on a slack line while others kayak, paddle board and canoe in Lake Calhoun in Minneapolis,

Photo: JENN ACKERMAN, STR

Where a Walk in the Park Is Never Far Away

If you live in Minneapolis, there's a 95 percent chance you live within a 10-minute walk to a park.

That bragging right and a few others make the city's park system the best among the 100 biggest cities in the country.

Minneapolis earned 86.5 out of 100 on the fifth annual ParkScore, just beating out its next-door neighbor, St. Paul, in a ranking of urban park systems published by the Trust for Public Land. The group rates cities on several criteria, including the percentage of residents who live near a park, size of the parks and per capita spending on parks.

Houston ranked 78th with a score of 41.

Tied for 10th place with Madison, Wis., was Cincinnati, an industrial powerhouse in the 19th century with parks that rival those of older East Coast cities. It has more than 5,000 acres of park land.

In the last year, the number of off-leash dog parks in the 100 biggest cities has increased by 4 percent, to a total of 684.

Tatiana Schlossberg

Frogs That Escaped Extinction

The Amazon gladiator frog is a fighter. But it could become a ghost.

Extinction threatens 40 percent of amphibian species worldwide. Since 1980, more than 200 species have disappeared as a result of habitat loss, killer fungi, viruses, pollution - and the exacerbation of these threats by climate change. But in recent years, some amphibians thought to be lost have, in a sense, returned from the dead, escaping extinction for now. In 2014, photographer Robin Moore published a book about them, "In Search of Lost Frogs."

The search hasn't been easy. In 2011, it took scientists eight months to find the Borneo rainbow toad in Malaysia's rain forest. They had only a scientific illustration and didn't know its color.

The poster child of lost frogs is the variable harlequin, rediscovered in Costa Rica in 2003 after chytrid fungus was thought to have decimated the species. The frog lives only in two populations along one stream in a remote private reserve in Costa Rica.

Moore had no luck finding the Mesopotamia beaked toad, last seen in 1914 in the Choco forests of Colombia. But he did discover what may be a new species. It has been widely compared to Monty Burns, Homer's boss on "The Simpsons."

Joanna Klein

Clouds Over Manhattan's Sun-Friendly Streets

Sunset lovers, your Instagram feeds will have to wait. A cloudy sky last weekend ruined the year's first opportunity to photograph Manhattanhenge, where the setting sun aligns perfectly with the numbered streets running east and west.

Normally the event bathes traffic and skyscrapers with warm red light, but on Sunday, it was just gray. Spectators gathered, hoping to catch the sun descending along city streets. The outlook for Monday night was not promising, either.

Here's the good news: Manhattanhenge happens twice a year, on opposite sides of the summer solstice, so you'll have a second chance to earn social media fame on July 11 and 12.

The spectacular alignment results from the arrangement of the city's cross streets two centuries ago, according to Jackie Faherty, an astrophysicist at the American Museum of Natural History.

"In the 1800s, when they made these 90-degree angles, they created a bull's-eye for the sun to hit," she said.

Nicholas St. Fleur

Triplet and Higher-Order Births in U.S. Down 41 percent

The rate of triplet and higher-order births rose rapidly during the 1980s and 1990s, but that trend has ended.

According to a new report from the National Center for Health Statistics, the rate of triplet and higher-order births plunged 41 percent from 1998 to 2014. More than 90 percent of these births are triplets.

Almost all of the decline occurred among women 25 and older, particularly women 45 and older, a drop of 67 percent to 769.9 per 100,000 births from 2,326. Non-Hispanic white women had the largest drop, about 46 percent.

But rates of triplet or higher-order births were still 57 percent higher in this group than among non-Hispanic blacks, and more than twice as high as the rate among Hispanic women.

The decline was nationwide. Only Oklahoma and Louisiana had increases in the number of triplets, and even there the increases were small - 8 percent in Oklahoma and 4 percent in Louisiana.

Older mothers are more likely to have a multiple birth, and the increase before 1998 was largely attributed to rising average maternal age, according to the lead author, Joyce Martin, a statistician with the NCHS.

"Age of mothers has continued to increase," she said, "so you would expect the rate of triplets to increase. So the decline cannot be attributed to any changes in maternal age."